Prevent PageUp and PageDown press in textarea moving website out of the window

index.js

// @see http://www.competa.com/blog/chrome-bug-pageup-pagedown-textarea-moves-website-window/
// @see https://bugs.chromium.org/p/chromium/issues/detail?id=890248
document.querySelector('textarea').addEventListener('keydown', event => {
  if (event.key === 'PageUp' || event.key === 'PageDown') {
    const cursorPosition = event.key === 'PageUp' ? 0 : event.target.textLength;

    event.preventDefault();
    event.target.setSelectionRange(cursorPosition, cursorPosition);
  }
});